This invention relates to measuring instruments and methods and is particularly directed to instruments and methods used to measure the size and dimensions of heart valves in the surgical operating room at the time of heart valve reconstruction or replacement.
When a surgeon must replace one or more of a patient""s heart valves because of disease or defect of the native valve(s), the surgeon must identify the diameter of the patient""s aorta in order to select the correct size replacement heart valve. The measurement of heart valve diameter in the operating room is typically done with some type of plug gauge. Gradated sizes of plug gauges, typically in 2 millimeter increments are used to find the best fit for any given valve annulus. The advent of homograft valves and, more recently, methods for reconstructing heart valves, makes it desirable to determine more than simply the best fit diameter. For operations involving the use of homograft valves, stentless heterograft valves, and any one of several methods of aortic or pulmonic heart valve reconstruction being used, it is also desirable to assess the height of the leaflets, the distance between the commissures and the symmetry, or lack thereof, of the spacing of the valve commissures. Such methods of valve reconstruction are described, for example, in Love U.S. Pat. No. 5,716,399, Love U.S. Pat. No. 6,129,758, and copending U.S. application Ser. No. 09/330,689 of Love, et al. (each of which is incorporated herein by reference in its entirety). To facilitate such methods of valve reconstruction, there is a strong need for instruments and methods that can be used in the operating room to quickly and effectively assess valve annulus geometry more completely than has been possible in the past. The instruments and methods of the present invention satisfy these needs and provide other advantageous results.
The present invention is comprised of methods and instruments that can be used to measure the diameter of the valve annulus at the commissural level, the sino-tubular diameter, to compare the height and lines of attachment of the individual leaflets with reference to a normalized geometry, and to determine the symmetry of the valve commissures.
One preferred embodiment of the present invention comprises a circular piece with three equally spaced radial spokes that converge in the center to a socket to which a handle can be attached. Curved legs that correspond to the geometry of the normal native valve leaflet anatomy, as described in published medical articles, are attached to the circular piece.
In a typical operation to replace or to reconstruct an aortic or pulmonic valve, the diseased native valve is removed down to the annulus of the valve. After this has been done, the valve is sized. With the present invention, sizers of graded dimensions are used until the best-fit diameter at the commissural level is determined. With that sizer inserted in the aortic or pulmonic root, the height of each leaflet from its base to the apex of its commissures can be compared with the expected dimensions for that valve, based on published dimensions. The symmetry of the valve can be judged by aligning any given radial spokes of the circular piece with one commissure, and then noting the spacing of the remaining two commissures. The radial spokes each have a width that corresponds to an arc of the circle that encompasses the normal expected variation from perfect symmetry. Deviations from expected normal leaflet height or symmetry can be readily appreciated and used to increase the precision of the planned surgical procedure.
Another version of the present invention includes a handle portion for holding the sizer and a sizing portion adjoining the handle portion. In one embodiment, the sizing portion has a predetermined distance indicator for assessing the distance between the commissures of the annulus. The sizing portion is placed adjacent to two of the commissures and the predetermined distance on the sizing portion is compared to the distance between the two commissures. In another embodiment, the sizing portion has a predetermined height indicator for assessing the leaflet height of the annulus. The sizing portion is placed along the contoured line of valve leaflet attachment of the annulus so that the predetermined height on the sizing portion can be compared to the leaflet height of the annulus.
A presently preferred embodiment includes an arch-shaped sizing portion substantially conforming to the shape of the contoured line of valve leaflet attachment of the annulus. The sizing portion is in the shape of an arch having an apex and two legs, each of which has a base adjoining the handle portion. The base of each leg is preferably bent such that the sizing portion is angled to conform to the conical shape of the valve annulus. The legs of the arched sizing portion are separated from each other by a predetermined distance. The predetermined distance separating the legs corresponds to the expected separation of commissures of a normal heart valve annulus having approximately the same diameter as the valve annulus being assessed. The height of the arch (measured from the base of each leg to the apex) preferably corresponds to a predetermined leaflet height. This predetermined height preferably approximates the expected height of a leaflet of a normal heart valve having approximately the same diameter as the valve annulus being assessed.
The distance between the commissures is assessed by inserting the sizing portion is into the heart valve annulus and placing the two legs of the arch adjacent to two of commissures of the valve annulus. The distance between the two commissures is compared to the predetermined distance between the two legs. For a tri-leaflet valve, symmetry can be assessed by comparing the three intercommissural distances; in a symmetric root these distances should be in close agreement. Leaflet height is assessed by placing the sizing portion of the device along the contour of the line of valve leaflet attachment and comparing the leaflet height of the heart valve annulus to the height of the arch.
The present invention further encompasses an instrument and method for marking a contoured line of valve leaflet attachment of a heart valve annulus. The instrument includes a handle portion and a marking portion. The marking portion conforms in shape to the contoured line of valve leaflet attachment and preferably includes a wettable textured region for retaining a marking material such as a dye. A marking material is applied to the marking portion. The marking portion is then inserted into the annulus and placed along the contoured line of valve leaflet attachment to mark the line of leaflet attachment.